On my Xbox live account, it says I'm not old enough to write a bio. Is there any way I can fix that so I can write a bio?
This is actually linked to your hotmail account that you used to sign up for xbox live with, that is the problem here and the only way you can change that is going into those settings..I believe.
You would have to make new account
change ur age?
No. Once you set your age below 18, there's no way to change it. Either make a new account or wait till you're of age.